If empty strings ("") should be allowed as key names. By default, the
driver will throw an exception if you attempt to pass the empty string as
a key to the database. It is extremely easy to do this inavertently by
using double quotes with $-operators, so it is recommended that you leave
this setting as default. However, if you need to save keys that are empty
strings, you can set this option to true and the driver will allow you to
pass empty strings to the database.

For replicaset connections: The minimum interval with which the driver
will send "isMaster" requests to the MongoDB server. If the value is lower,
there will be more requests, but the driver finds faster whether the
topology of the replicaset has been changed.

The default behavior for this has been changed to TRUE in 1.5.0, so make
sure to set this variable to the value you want (probably TRUE) so that
the driver's behavior doesn't suddenly change when you upgrade.

On 64-bit platforms, the mongo.native_long setting
allows for 64-bit integers to be stored in MongoDB. If it is not set, only
32-bits of the integer will be saved. The MongoDB data type that is used
in this case is the BSON LONG, instead of the BSON INT that is used if
this setting is turned off.

The setting also changes the way how BSON LONGs behave when they are read
back from MongoDB. Without mongo.native_long enabled,
the driver would convert every BSON LONG to a PHP double which can result
in a loss of precision.

On 32-bit platforms, the mongo.native_log setting
changes nothing for storing integers in MongoDB: the integer is stored
as a BSON INT as before. However, when the setting is enabled and a
BSON LONG is read from MongoDB a
MongoCursorException is thrown alerting you that
the data could not be read back without losing precision.

On 32-bit systems especially, it is recommended that you combine this with
enabling mongo.long_as_object.

For replicaset connections: The minimum interval with which the driver
will send "ping" requests to the MongoDB server. If the value is lower,
there will be more pings, but the driver finds faster whether a node is
no longer reachable from the replicaset.

If an exception should be thrown for non-UTF8 strings. Until version
1.0.4, the PHP driver would ignore non-UTF8 strings, even though you're
not supposed to insert them. As of 1.0.4, the driver throws a
MongoException. To ease the transition for
applications that insert non-UTF8 strings, you can turn this option off to
emulate the old, non-exception-throwning behavior. This option will be
eliminated and exceptions always thrown for non-UTF8 strings starting with
version 1.1.0.